In two studies (N = 1,747; N = 701), cross-sectional data from Canada and America were gathered from college-students and MTurk (respectively) to understand the relationship between the age of the participant and scores on the Dark Triad traits (i.e., narcissism, psychopathy, and Machiavellianism). Age had a number of important effects on Dark Triad traits. First, older samples scored lower on the narcissism and psychopathy; effects that were stronger in men than in women. Second, age was negatively correlated with the Dark Triad traits; associations that were generally uniform across the sexes. Third, the variance between scores on each trait was larger at younger ages than older ones in both sexes. These results are consistent with and discussed within a Life History approach on the Dark Triad traits taken by some evolutionary psychologists studying these traits.

One of the traditional, defining features of personality traits is their consistency over the life course. A number of mechanisms have been proposed to account for this supposed stability (for review see [Roberts, DelVecchio, 2000]). For instance, it might be because people experience a stable environment. It might be because personality traits are heritable and genes as reasonably fixed throughout someone’s lifetime, as suggested by behavioral genetics. It could be the result of a movement from immature to mature disposition, as per psychoanalytic theory. And, last, it could be caused by the gradual solidification of people’s personality trait as they age. However, all of these seem untenable given some sweeping and thorough studies that clearly indicate personality change over the life course [McCrae et al., 1999; Roberts, DelVecchio, 2000; Roberts et al., 2006; Soto et al., 2011]. For example, social dominance scores appear to go up as people get older [Roberts et al., 2006] whereas intrinsic motivation goes down [Lepper et al., 2005].

Research on personality change over the life course has covered various individual differences like Eriksonian traits [Zucker et al., 2002], the Big Five traits [McCrae et al., 1999], emotional regulation strategies [Holen-Hoeksema, Aldao, 2011], the California Personality Inventory traits [Labouvie-Vief et al., 2000], extrinsic and intrinsic motivations [Lepper et al., 2005], and sensation seeking and impulsivity [Steinberg et al., 2008]. Nevertheless, the vast majority of research has examined the correlations between age of the participant and the Big Five traits (e.g., [Soto et al., 2011]). However, today, much attention is being paid to the Dark Triad traits (i.e., psychopathy, narcissism, and Machiavellianism) as a means to study the "darker" side of human nature to compliment the rather "light" traits found in the Big Five.

The Dark Triad traits [Jonason, Li, Webster, Schmitt, 2009; Paulhus, Williams, 2002] are characterized by entitlement, superiority, dominance (i.e., narcissism), glib social charm, manipulativeness (i.e., Machiavellianism), callous social attitudes, impulsivity, and interpersonal antagonism (i.e., psychopathy). Research has examined these traits in various domains like mating [Jonason, Valentine, Li, Harbeson, 2011], friendship [Jonason, Schmitt 2012], and vocational interests [Jonason, Wee, Li, Jackson, 2014]. To date there have been few studies that have examined whether the Dark Triad traits change over the life course. When done, the studies rarely examined all three traits simultaneously [Foster et al., 2003], often break up age into relatively arbitrary age groups [Mudrack, 1989], are concerned with the emergence of the Dark Triad traits from childhood [Lyman et al., 2007], relied on college-student samples [Twenge et al., 2008], and relied on particular measures of the traits [Foster et al., 2003].

Despite these limitations, a number of studies suggest people’s psychopathy [Harpur, Hare, 1994], Machiavellianism [Mudrack, 1989; Murray, Okannes, 1980], and narcissism scores decrease with age [Foster et al., 2003; Wilson, Sibley, 2011], and one report suggested older samples score lower on the Dark Triad (using only a composite score) than younger ones [Jonason, Slomski, Partyka, 2012]. Studies have overtly shown that the Dark Triad traits are negatively correlated with participant’s age [Aghababaei et al., 2014; Fox, Rooney, 2015] appear to have explored age in a descriptive fashion. Beyond work on the Dark Triad traits in particular, a number of other studies converge on the same point. The Dark Triad traits are correlated with self-control and impulsivity [Jonason, Tost, 2010; Jones, Paulhus, 2011] and agreeableness [Jonason, Webster, 2010]. As conscientiousness appears to go up as people age and agreeableness goes down as people age [McCrae et al., 1999; Soto et al., 2011], it seems reasonable to expect age effects on the Dark Triad traits. And finally, if one thinks of cynicism as the opposite of trust, research on aged samples tendency to be more trusting than younger samples [Bailey et al., in press; Poulin, Hasse, 2015] might suggest those who are older may score lower on traits that have cynicism at their core like the Dark Triad traits [Jonason, Webster, 2010].

There might be good theoretical reasons to predict age declines. As yet, theoretical reasons for age effects have tended to rely on proximal, social psychological and developmental psychological models to frame the effects. Indeed, much of the work on age effects tends to be relatively descriptive in nature (e.g., [ Soto et al., 2011]). In contrast, the Dark Triad traits have been successfully integrated into a life history perspective, allowing for a particularly understanding of the ultimate, evolutionary origins of the "darker" sides of human nature (for review see, [Jonason, Webster, Schmitt, Li, Crysel, 2012; Rushton, 1985; 1995]).

From a Life History Theory perspective, one might conceptualize age effects in the Dark Triad traits as part of the deceleration of individual’s life history strategies as they mature. Individuals may invest more energy into mating effort when younger. In particular, at prime mating time in people’s lives, individuals may invest heavily in mating effort, and the Dark Triad traits appear to facilitate just such a fast approach to the world [Jonason, Koenig, Tost, 2010; Jonason et al., 2009; 2011]. The period of life between 18 and 30 contains peaks (and subsequent declines] in various traits that may facilitate mating effort like impulsivity, selfishness, competiveness, and, perhaps the Dark Triad traits as well [Arnett, Taber, 1994; Peach, Gaultney, 2013]. Indeed, increases in agreeableness and conscientiousness [Soto et al., 2011] may also reflect a transition from agentic to mutualistic life history strategies. It is during this portion of their lives that people may reap the most fitness benefit from having these traits and once this period is passed individuals may transition out of this approach to life. The value of having this approach to life may diminish over the life course and even cost individuals who are older relative to those who are younger (e.g., they may have more to lose). As people transition to somatic effort, traits like the Dark Triad might interfere with such a lifestyle (e.g., long-term mating, child-bearing, child-rearing). This means that over the life course people should adopt a slower life history strategy and this will pull down their Dark Triad scores.

While it is reasonable and logical to expect decreases in the individual’s scores on the Dark Triad traits, there may also be reason to expect coherence to increase with age. One model of personality change suggests that people consolidate their profile across the life course. Indeed, when examining the Big Five, the correlations between two time points when people are older are better correlated than when examining equidistant time points at younger ages [Roberts, DelVecchio, 2000]. The Dark Triad traits may differentially equip individuals with various social skills to exploit others [Jonason, Webster, 2012]. As people age, the value of the Dark Triad traits may diminish because exploitation is less important than mutualistic goals. Indeed, the Dark Triad traits are associated with selfish and anti-group sentiments [Jonason, Duineveld, Middleto, 2015; Jonason, Strosser, Kroll, Duineveld, Baruffi, 2015]. A byproduct of the general decline in the adaptive value of these traits might be a range restriction in the discrepancy between the scores, leaving everyone scoring particularly low on each trait. Therefore, increased cohesion within participants in their Dark Triad trait scores is expected.

This study presents the first analysis of the age effects on the Dark Triad traits as a collective using an evolutionary-developmental hypothesis (i.e., Life History Theory). It is also the first to assess these effects using two different measures of the Dark Triad traits. And lastly, it examines whether participant’s sex moderates age effects.

Study 1

In this study, attention is paid to age effects and the Dark Triad traits. In particular, samples of Canadian college students and American MTurk participants are combined to examine age effects across sample-type but also overall and in each sex. This is important because prior studies suggest the association between the age of the participant and traits like Machiavellianism may only be detectable in "older" samples [Mudrack, 1989] and prior research highlights the importance of comparing early and middle adulthood samples [McCrae et al., 1999].

Method

Participants and procedure. Three previously published [Baughman et al., 2014; Jonason, Duineveld, Middleton, 2015; Middleton, 2014] and three, as yet, unpublished datasets [Baughman, 2014; 2015; Girgis, 2014] [1] were collected and collated to reduce range restriction in age in any one sample, thereby increasing power. The sample was composed of 941 Canadian students [33% male) aged 16–54 (M = 18,43; SD = 2,31) who received partial course credit for participating in an online study and 806 Americans (33% male) aged 17–76 (M = 32,84; SD = 11,19) who received US$1 for their MTurk participation in various online studies. The former was a modestly younger sample than the latter (t(1741) = –4,75, p < ,01, Cohen’s d = –0,23). Participants were informed of the nature of each study (all were correlational and cross-sectional studies on topics like sexuality, organizational psychology, or personality psychology), they completed a series of self-report measures (≈15 minutes), and then were debriefed and thanked for their participation.

In order to test the coherence among the Dark Triad traits across the life course, an additional variable was calculated. The squared variances between the scores of each of the Dark Triad traits (i.e., the residuals) were summed and then divided by three. This translates into a measure of within-person variance in Dark Triad trait scores.

Where P = participant’s score on psychopathy; M = participant’s score on Machiavellianism; N = Participant’s score on narcissism. Importantly, this gets around the problem of comparing the two samples for age effects as they are from two different countries and from two different sources, which creates an ostensible confound in conclusions between the groups.

When examining the relationship between the age of the participant and the Dark Triad traits a few things were clear (Table 1). First, as people age their Dark Triad traits appear to decelerate. Second, this pattern appears similar in men and women. Third, this deceleration can only be detected in an older sample. This is consistent with the contention that the Dark Triad traits are a coordinated system for short-term mating effort used during the primary, ancestral reproductive period of ancestral humans. Importantly, however, this analysis reveals a significant, albeit weak negative correlation for Machiavellianism. This effect may reveal the superior nature of maximizing variance in continuous data (e.g., age) over examining relatively arbitrary categories.

Table 1
Association between participant's age and the Dark Triad traits and in college student and MTurk samples

Last, as the variance within-participants in their Dark Triad scores went up so did their age (r(1745) = ,08, p < ,01); an effect that was stronger in women (r = ,12, p < ,01) than in men (r = ,02) and present in older participants (r = ,07, p < ,05) but not younger ones (r = ,01). This suggests that the purportedly coordinated system that is the Dark Triad breaks down as people age, especially in women. That is, there is more variance in individual’s scores in the Dark Triad traits when they are older as opposed to younger. However, as these effects are extremely small, they will need to be replicated.

Study 2

While results in Study 1 were consistent with previous literature and with the evolutionary-developmental logic laid out, it was limited in two important ways. First, it relied on only one measure of the Dark Triad traits. Second, the analyses conflate age of sample with both location and incentive. Third, it relied on datasets that were cobbled together as opposed to collected all at once, which may introduce unmeasured variance. Therefore, in Study 2, the associations between the Dark Triad traits and the age of the participant were reexamined using the Dirty Dozen measure in a single large-scale project. In other words, Study 2 is a conceptual replication testing the methodological robustness of the effects reported in Study 1.

Method

Participants. As results above suggest, the age effects are best detected in samples with a higher mean age. Therefore, only an MTurk sample was used in this study.[3] The sample was composed of 701 (48% male) Americans, aged 13–76 (M = 32,54, SD = 11,42). Participants received US$2 for participating in a study on political attitudes and behaviors.

Measures. To measure the Dark Triad traits, the Dark Triad Dirty Dozen (Jonason, Webster, 2010] was used. Participants were asked how much they agreed (1 = not at all; 5 = very much) with statements such as: "I tend to want others to admire me" (i.e., narcissism), "I tend to lack remorse" (i.e., psychopathy), and "I have used deceit or lied to get my way" (i.e., Machiavellianism). Items were averaged together to create an index of narcissism (Cronbach’s α = ,81), Machiavellianism (α = ,80), and psychopathy (α = ,70).[4]

Again, in order to test for coherence within the Dark Triad traits, the same variable as above was calculated. Importantly, as this is just one sample, it should provide a better test of the coherence than in Study 1. The expectation is that participants will have greater coherence as they age, because their personality is likely to solidify.

Results and Discussion

When correlating the Dark Triad traits with participants’ age, results largely confirm those from Study 1. Psychopathy (r(699) = –,20, p < ,01), Machiavellianism (r(699) = –,20, p < ,01), and narcissism (r(699) = –,29, p < ,01) decreased as people got older. These effects were equivalent in both sexes with the exception of the correlation being absent in men (r = –,08) and present in women (r = –,25, p < ,01) only in psychopathy (Fisher’s z = –2,31, p < ,05). As seen in Figure 3, there was a general, linear, deceleration of the Dark Triad traits but it appears that the deceleration in narcissism starts sooner and is generally consistent throughout people’s lives whereas psychopathy and Machiavellianism appear to plateau in sync until the 30s and then have a decline after that.

Figure 3. Deceleration of scores on the Dark Triad traits as a function of participant’s age in Study 2.

Lastly, there was strong evidence for increased coherence of the Dark Triad trait scores in people. The coherence measure was correlated with participant’s age (r(699) = –,30, p < ,01), suggesting that as people age the variance (i.e., residuals) between their scores on each trait goes down. These correlations were virtually identical in men (r = –,26, p < ,01) and women (r = –,30, p < ,01). This suggests results from Study 1in relation to coherence over the life course are untrustworthy and wrong.

General Discussion

The Dark Triad traits have become a major area of personality research may be one of the major areas [Jonason et al., 2012] to rival other areas of research like the Big Five and motivational systems. Researchers have examined various intrapersonal [Jonason, Tost, 2010], interpersonal [Jonason, Schmitt, 2012], and behavioral [Jones, Paulhus, 2010] correlates of these traits but whether there are age effects on these traits has been limited. There is considerable research suggesting that there is a general trend to mutualistic traits like increased agreeableness and conscientiousness [Soto et al., 2011] and there might be good theoretical reason, provided by Life History Theory [Wilson, 1975], to expect a deceleration in the Dark Triad traits over the life course [Wilson et al., 1996].

There are two primary findings in this study. Whether measured with the Dirty Dozen [Jonason, Webster, 2010] or the Short Dark Triad [Jones, Paulhus, 2014], all three of the Dark Triad traits showed a slow but significant deceleration in Dark Triad trait scores overall and in both sexes. From a life history perspective, traits that facilitate mating effort should peak between 18 and 30 years of age. Indeed, psychopathy increases from childhood to adulthood [Lyman et al., 2007] and, as the present study suggests, declines after this period along with Machiavellianism (see Figure 3). Such decreases mirror age declines in other life history traits like impulsivity [Snowden, Gray, 2011; Steinberg et al., 2008]. In contrast, little change in Dark Triad trait scores was observed at younger ages. Not only does this suggest that research relying solely on college student samples [Twenge et al., 2008] might be looking in the wrong place (most likely because it is atheoretical, descriptive work), but it has implications for the types of life changes that may co-occur with the deceleration of fast life history strategies (e.g., marriage, child-bearing, child-rearing). The deceleration of fastlife history traits might merely be part of the near-inevitable maturation of people as they transition from mating effort to somatic effort and selfish agendas to mutualistic ones. In addition, the fact that the Dark Triad traits are sensitive to potential contextual and motivational changes over the life course, is consistent with the evolutionary approach as opposed to the standard pathological approach that conceived of such traits as ubiquitously problematic.

Secondarily, there appears to be an increased coherence as people age between the Dark Triad traits within individuals. While inconsistent across studies, Study 2 strongly suggests that as people age the standardized residuals between individual’s scores on each of the Dark Triad traits gets smaller. This may be a by-product of the range restriction created by the global deceleration of these traits over the life course. As people age, they may consolidate their personality by investing into a single, coherent life history strategy that better reflects mutualistic concerns over selfish (and as psychoanalysts would suggest, childish) agendas. At younger ages, the Dark Triad traits may represent agentic and antisocial approaches to people [Jonason, Strosser et al., 2015]. While past research has focused on coherence personality over time [Roberts, DelVecchio, 2000], this study focused on the coherence of the purported coordinated system of the Dark Triad traits [Jonason et al., 2009; Jonason , Webster, 2012].

Limitations and Conclusions

The primary limitation of this paper is that it was secondary data analysis, despite secondary data analysis being common practice for examining age effects [McCrae et al., 1999]. One problem this presented here was some variance in the degrees of freedom because of missing data. Given the sample sizes in the studies along with the use of maximum likelihood estimation, such concerns should be of little concern. The real problem with the use of secondary data analysis is that little can be said for the mechanisms of change because no such data was collected. However, there are some likely proximal (developmental psychological) and ultimate (evolutionary psychological) candidates. Emerging adulthood (e.g., 18–30 years of age) may be a time of identity exploration, experimentation, and uncertainty around role transitions [Arnett, 2000; 2001]. These factors may account for the declines—albeit small—observed in Dark Triad trait scores found here. Alternatively, what maturation may represent is a switching from fast life history approaches to slow(er) life history approaches. Indeed, the very transitional factors noted by developmental psychologists (e.g., marriage, parenthood; [Arnett, 2000]) and social psychologists (e.g., impulse control; [Rose, 2007; Snowden, Gray, 2011]) represent characteristics of someone engaging in a slower life history strategy than a fast one. In both cases, prior research is consistent with these contentions with improved impulse control, behavioral control, and quality decision-making in older samples [Arnett, Taber, 1994; Peach, Gaultney, 2013].

The second problematic nature of this study is its reliance on cross-sectional data which means the study does not necessarily examine personality change as opposed to potential cultural shifts. This means the study may suffer from cohort effects and small effects. While this is to be expected [McCrae et al., 1999], longitudinal studies might reveal stronger and cleaner effects as they are within-person methods. Nevertheless, both mean-level change and rank-order change studies suggest personality change is a real thing [Roberts, DelVecchio, 2000; Roberts et al., 2006; Soto et al., 2011]. Moreover, mean-level, cross-sectional designs are not an uncommon method to study age effects [Soto et al., 2011]. Nevertheless, there has yet to be a single longitudinal study on the Dark Triad traits. This is not surprising given the relative newness of the focus on these traits in subclinical psychology [Paulhus, Williams, 2002]. Future studies should disentangle any cultural shifts that might be responsible for high rates of the Dark Triad traits in younger generations and to assess genuine personality change with age.

In conclusion, this study provides a meaningful advance in the understanding of personality changes as a function of age by examining darker aspects of human nature in the form of the Dark Triad traits and framing the effects from an evolutionary-developmental perspective. Unlike prior work that either examined the three traits independently did not measure age continuously, relied on college-student samples, relied on a single measure of the Dark Triad traits, or were primarily descriptive, this study provides the first account of continuous change in the Dark Triad traits over the life course in college-aged and MTurk samples using two measures of the traits and a life history perspective. While more work is needed to ascertain what are the mechanisms and correlates of this change, this study acts as a proof of concept; there might a deceleration and increased cohesion among the Dark Triad traits in men and women as they age.

Acknowledgements
Thanks to Laura Mansfield for reviewing this paper before submission.

Middleton J.P. How food preferences reveal the opportunism in the Dark Triad traits. Talk presented at the Australian Conference on Personality and Individual Differences in Newcastle, NSW, Australia, 2014.

Roberts B.W., Walton K.E., Viechtbauer W. Patterns of mean-level change in personality traits across the life course: A meta-analysis of longitudinal studies. Journal of Personality and Social Psychology, 2006, 132(1), 1–25.

Rose P. Mediators of the association between narcissism and compulsive buying: The roles of materialism and impulse control. Psychology of Addictive Behaviors, 2007, 21(4), 576–581.

Rushton J.P. Race, evolution, and J. Age differences in sensation seeking and impulsivity as indexed by behavior and self-report: Evidence for a dual system model. Developmental Psychology, 2008, 44(6), 1764–1778.